Psychomotor learning, development of organized patterns of muscular activities guided by signals from the environment. Behavioral examples include driving a car and eye-hand coordination tasks such as sewing, throwing a ball, typing, operating a lathe, and playing a trombone. Also called sensorimotor and perceptual-motor skills, they are studied as special topics in the experimental psychology of human learning and performance. In research concerning psychomotor skills, particular attention is given to the learning of coordinated activity involving the arms, hands, fingers, and feet (verbal processes are not emphasized).

The range of skills

The term skill denotes a movement that is reasonably complex and the execution of which requires at least a minimal amount of practice—reflex acts such as sneezing are excluded. Research shows that the performance of complex skills can be influenced by sensations arising from the things the performer looks at, sensations from the muscles that are involved in the movement itself, and stimuli received through other sensory organs. Thus the term sensorimotor skill is used to denote the close relationship between movement and sensation involved in complex acts.

Simple components of bodily skills

Most of life’s skills are continuous and complex and contain a multitude of integrated components; however, these complex skills may be analyzed by examining their component parts. For example, skills may be measured by time intervals. In the laboratory, a subject’s reaction time is measured as the time between the presentation of some kind of stimulus and the performer’s initial response. The individual’s speed of reaction depends upon a number of variables, including the intensity of the stimuli. For example, a person will initiate a movement more quickly to increasingly louder sounds until a limit is reached. When the sounds become too loud, however, the noise delays the onset of the movement. A longer reaction time will also be recorded if the subject must choose among a number of stimuli before initiating a movement (such as moving only if one of a number of various coloured lights is turned on) or if the required act involves a complex movement.

The quality of the movement will depend upon such factors as the precision of the act required, the performer’s past experience with similar skills, the speed of the movement, the force of the motor act, and the body part or parts to be moved.

There are limits to the efficient performance of even the simplest motor skills. Finger tapping at more than 10 times per second, for example, is usually impossible. Individuals vary greatly in their ability to exercise force with various body parts. Studies of the human motor system also show that an individual rarely (if ever) repeats an apparently similar movement in precisely the same way. Thus the acquisition of skill in a given task involves the performance of a reasonably consistent response pattern, which varies, within limits, from trial to trial.

A number of basic motor abilities underlie the performance of many routine activities. One category of abilities may be broadly referred to as manual dexterity, which includes fine finger dexterity, arm-wrist speed, and aiming ability. Motor abilities are also influenced by strength, of which there are several kinds, including static strength (pressure measured in pounds exerted against an immovable object) and dynamic strength (moving the limbs with force). Flexibility and balancing ability are similarly divided into several components. Thus discussion of a single quality in human movement is inaccurate. One should refer instead to several specific types of ability.

Motor skills may also be classified by the general characteristics of the tasks themselves. Gross motor skills refer to acts in which the larger muscles are commonly involved, while fine motor skills denote actions of the hands and fingers. Most skills incorporate movements of both the larger and the smaller muscle groups. The basketball player uses his larger skeletal muscles to run and jump while drawing on fine motor skills such as accurate finger control when dribbling or shooting the ball.

Most of life’s skills are composed of several integrated parts. Such skills are often controlled by the organization of visual information available to the performer, particularly during the early stages of learning. At the same time, the individual’s ability to analyze the mechanics of a motor task, his verbal ability, and other intellectual and perceptual attributes may influence his acquisition of a skill.

Skills are susceptible to all kinds of limits. If there is sufficient genetic aptitude, a person’s mastery of a skill depends on his motivation to improve, on his receiving continuous information or sensory feedback about the adequacy of his performance during training, and on such factors as the rewarding effects of corrections made during successive practice periods. Some gains in proficiency can be masked by temporary losses but will emerge later.

Psychomotor habits are mediated primarily by the sensory and motor cortex of the brain and by the neural fibres that connect the two cerebral hemispheres. According to the majority of theoreticians, learning outcomes can be correlated with the amount or duration of rewarded practice. The effects of associative and motivational factors are believed to enhance learning, while inhibitory and oscillation (variability) factors are thought to detract from the learning of psychomotor skills.

Laboratory research in psychomotor learning

Devices and tasks

Most scientists study psychomotor learning under controlled laboratory conditions, which contribute to more accurate measures of proficiency and reduce the amount of variability in a learner’s performance as the training progresses. Hundreds of electrical and mechanical instruments have been developed for research in psychomotor learning, but only about two dozen are used with any regularity.

One device, a complex coordinator, measures the learner’s ability to make prompt, synchronized adjustments of handstick and foot-bar controls in response to combinations of stimulus lights. Another device, a discrimination reaction timer, requires that one of several toggle switches be snapped rapidly in response to designated distinctive spatial patterns of coloured signal lamps. In performing on a manual lever, a blindfolded subject must learn how far to move the handle on the basis of numerical information provided by the experimenter. With a mirror tracer, a six-pointed star pattern is followed with an electrical stylus as accurately and quickly as possible, the learner being guided visually only by a mirror image. The multidimensional pursuitmeter requires the learner to scan four dials and to keep the indicators steady by making corrections with four controls (similar to those found in an airplane cockpit). On a rotary pursuitmeter the learner must hold a flexible stylus in continuous electrical contact with a small, circular metal target set into a revolving turntable.

Also employed is the selective mathometer, a device on which the subject’s problem is to discover, with cues provided by a signal lamp, which of some 20 pushbuttons should be pressed in response to each of a series of distinctive images projected on a screen. While using a star discrimeter, a person receives information about his errors through earphones; the task is to learn to selectively position one lever among six radial slots in accordance with signals from differently coloured stimulus lights. A trainee on a two-hand coordinator has to manipulate two lathe crank handles synchronously to maintain contact with a target disk as it moves through an irregular course. Computers are now used for more precise measurements.

Measurements

The tasks required by the above devices produce a substantial range of psychomotor difficulty. The elements of skilled behaviour are expressed as numerical scores that measure response and error percentages, amplitude and speed of movement, hand or foot pressures exerted, time on target, reaction time, rate of response, and indices of time-sharing activity. Most of these measurements lend themselves to mathematical treatment. Laboratory devices for studying psychomotor learning can be useful in predicting performance in factory work and the operation of motor vehicles and aircraft. When properly maintained and used under standardized conditions, these perceptual-motor devices provide reliable measures of the activities they are designed to measure, and they also tap a significant proportion of the abilities required in real-life situations.

Phenomena of psychomotor learning

Acquisition

Speed and accuracy in the majority of psychomotor tasks studied are typically acquired very rapidly during the early stages of reinforced practice, the average rate of gain tending to drop off as the number of trials or training time increases (Figure 1). Curves based on such measures as reaction time or errors reflect the learner’s improvement by a series of decreasing scores, giving an inverted picture of Figure 1. Tracking scores from the two sexes are seen in Figure 1. Other devices have yielded more complicated functions—e.g., S-shaped curves for complex multiple-choice problems on the selective mathometer (Figure 2). Most acquisition curves obey a law of diminishing returns as high levels of skill are approached. Data such as those from tracking and multiple-choice tasks can be explained by rational mathematical equations derived from theoretical models (see formulas and captions in Figures 1 and 2). Between them, these two equations describe psychomotor acquisition curves from a wide variety of learning situations and of trainees with less than a 2 percent average error of prediction. Contrary to lay opinion, stepwise plateaus of proficiency are seldom seen.

The phenomena of generalization and transfer are seen in the tendency of laboratory subjects conditioned to respond to a particular stimulus to respond as well to similar stimuli beyond the original conditions of training. The measured effects of prior training on the performance of a subsequent task define the transfer of psychomotor learning. In practical skills, transfer is more likely to take place between tennis and badminton, for example, than between swimming and football, and between cornet and trumpet than between piano and tuba. Similarity of movement can facilitate transfer, as can the amount of practice or the sequence of events in previous training. The more the two situations have in common, the greater is the amount of predictable transfer. As differences increase between the stimuli used in training and those encountered on test trials, however, the effects of generalization decrease until there may be no transfer from one situation to another.

Learning one task may facilitate, hinder, or have no observable influence upon performance of the next task, meaning that transfer effects may be positive, negative, or null. Flight simulators are designed to maximize the amount of positive transfer, often by ensuring high levels of behavioral similarity. Negative transfer effects (such as reaching for the floor to shift gears when the shift lever is on the steering wheel) appear occasionally but tend to be easily overcome. Since transfer necessarily involves retention, the best schedules minimize forgetting by minimizing the time between training and transfer.

The degree and amount of transfer are contingent upon such factors as number of common elements or principles, stimulus and response similarity, amount of predifferentiation training, the variety of learning-to-learn experiences, part-to-whole relationships, differences in intertask complexity, use of mnemonic aids, and the extent of proactive or retroactive interference. Retroactive interference designs typically employ a sequence of original learning, interpolated learning, and relearning.

Retention

Learning is to acquisition as memory is to retention. Psychomotor retention scores indicate the percentage or degree of originally learned skill that is remembered or recalled as a function of elapsed time. Alterations of motor memory are identified by changes in means, variances, and correlations between test results. In contrast to verbal behaviour (which is susceptible to forgetting through interference within a matter of seconds), mean scores for tracking and coordination skills recorded over periods ranging from two days to two years diminish scarcely at all. Yet, when intervals of three minutes to six weeks are interpolated between discrete responses on a manual lever device, performance remains stable for about two days and then becomes inconsistent; variabilities increase and correlations decrease as the subjects mis-recall more and more of their original skill. In the light of this evidence, motor memory may be viewed as a phenomenon of persistence, while forgetting is a case of inconsistence.

One hypothesis advanced to account for the greater retentivity of psychomotor behaviour, as compared to that of newly acquired verbal behaviour, is that nonverbal actions are more often overlearned and are less susceptible to proactive interference (i.e., competition arising from things learned in the past). Distinctions between immediate, short-term, and long-term memory are also less prominent in studies of motor learning. This is not to say that motor skills are unforgettable; studies of short-term memory suggest that psychomotor forgetting can be swift indeed. Regardless of theoretical differences, however, psychologists generally agree that psychomotor behaviour is best remembered (and least forgotten) when overlearning is high, interference is low, reinforcing feedback is optimal, and interpolated activities are unrelated to the task being learned. Time is less important in the degradation of memory than are the events that fill the time.

Reminiscence

Reminiscence is defined as a gain in performance without practice. When subjects performing trial after trial without rest (massed practice) are given a short break, perhaps midway through training, scores on the very next trial will show a significant improvement when compared with those of a massed group given no break. Reminiscence effects are most prominent in tasks demanding continuous attention and response. Reminiscence also manifests as a bilateral transfer of skill (e.g., from the left to the right hand), suggesting that this phenomenon is controlled by the central nervous system.

Warm-up

Athletes and musicians often report that they get “cold” during a break from the activity (even for a rest period of a mere five minutes); when practice resumes, a warm-up period appears to be an intrinsic requirement of efficient performance. Wherever reminiscence goes, warm-up seems to follow; yet the converse does not always hold. The connection between warm-up and forgetting is uncertain.

Refractory period and anticipation

When required to make quick, discrete responses to two stimuli separated in time by one-half second or less, an operator’s reaction time (latency) for executing the second response is typically longer than that of his first response. This difference in reaction time is called the psychological refractory period.

Expectancy may occur, for example, when a subject has come to expect a delay between the first and second stimulus, meaning the subject will be relatively unprepared should the second arrive earlier than usual. Furthermore, people learn to expect certain kinds of stimuli over others. Performance declines when a person is uncertain about whether regularly occurring stimuli will be auditory or visual, or when the spatial direction of a stimulus is uncertain. This would suggest the possibility of divided attention; indeed, when pairs of stimuli are made perfectly predictable as to time and type, no impairment of response is observed.

If a subject can acquire suitable expectancies via training and experience, then he can improve the skill of dividing his attention and, within physiological limits, simultaneously handle an increased range of stimuli without a loss of proficiency. Given enough practice, people can reduce the psychological refractory period. A military gunner scanning a distant fixed target for its horizontal and vertical location, for example, is engaging in a preview of receptor anticipation to maximize his score. An operatic soprano who rehearses covertly the opening notes of her cadenza while the orchestra finishes the introduction is employing perceptual anticipation to optimize her performance. Anticipatory timing is learned, and reinforcing feedback is necessary.

Factors affecting psychomotor skill

Amount of practice

It has been noted above (Figure 1) that the practice of sensorimotor tasks usually produces changes in scores that reflect diminishing returns. A major influence in learning generally, repetition is the most powerful experimental variable known in psychomotor-skills research. But practice alone does not make perfect; psychological feedback is also necessary. The consensus among theoreticians is that feedback must be relevant and reinforcing to effect permanent increments of habit strength.

The effects of feedback and four other important performance variables (i.e., task complexity, work distribution, motive-incentive conditions, and environmental factors) remain to be summarized.

Psychological feedback

Ranking prominently among experimental variables are so-called feedback contingencies (aftereffects, knowledge of results) that may be controlled by the experimenter so as to occur concurrently with or soon after a subject’s response. A learner appears to improve by knowing the discrepancy between a response he has made and the response required of him; but, in experimental practice, the investigator manipulates behaviour by transforming functions of error. Since transformations are usually numerical or spatial, sensory returns from one’s action may be informative, motivating, or reinforcing. Response-produced stimulation is intrinsic to most skeletal–muscular circuits; the neural consequences of bodily movement are fed back into the central nervous system to serve the organism’s regulatory and adaptive functions. When this normal feedback is interrupted or delayed, psychomotor skill is often seriously degraded. Experimentally delayed auditory feedback of a subject’s oral reading produces stuttering and other speech problems; delayed visual feedback in simulated automobile steering is a greater hazard under emergency conditions than is the driver’s reaction time.

Laboratory investigations have supported the following generalizations about psychomotor learning: (1) without some kind of relevant feedback, there is no acquisition of skill; (2) progressive gains in proficiency occur in the presence of relevant feedback; (3) performance is disrupted when relevant feedback is withdrawn; (4) delayed feedback in continuous (but not discrete) tasks is typically decremental; (5) augmented or supplementary feedback usually results in increments; (6) the higher the relative frequency of reinforcing feedback, the greater is the facilitation of skill; and (7) the more specific the feedback (e.g., in designating location, direction, amount), the better is the performance.

Experiments with a manual lever device, for example, suggest that when feedback is introduced and withdrawn at four stages of practice, the effect on error scores is profound. Knowledge of results given early and late has effects similar enough to reject any hypothesis that learning arises merely from repetition. These experiments indicate that practice makes perfect only if reinforced; the result of unreinforced practice is extinction of the correct response and a proliferation of errors. Studies employing a complex mirror-tracking apparatus have clarified the role of reinforcing feedback. Targeting performance was facilitated by presenting distinctive supplementary visual feedback cues previously associated with aversive (electrical shock) and nonaversive consequences. Moreover, the amount of facilitation grew curvilinearly with the number of cue conditioning trials. Work on human incentive learning thus demonstrates that the rate of gain in psychomotor proficiency can be regulated by stimuli that have been accompanied by positive or negative aftereffects. Persistence of the acquired reinforcing effects, considered with their cumulative quantitative properties, enhances the attractiveness of theoretical interpretations that emphasize continuity and reinforcement as contrasted with theories based on discontinuity and contiguity alone. Clark Hull’s system (1943) is the classic model.

Task complexity

The complexity of discrete psychomotor tasks may be specified either as the number of response sequences a subject can make or as some measure of a subject’s uncertainty about choices among stimuli. Still other factors that have been investigated as instances of complexity include variations in the number of possible responses at each choice point, different lengths of series, and regular versus unpredictable stimulus sequences.

Experimental procedures involving an increase of complexity produce more errors, require more trials to reach proficiency, and result in longer latencies per trial. Difficulty in psychomotor learning, therefore, generally increases with the complexity of the task to be mastered. An example of this phenomenon appears in Figure 2. Subjects exhibit continually altered probabilities of response during training sessions, and an average person with enough practice on a discrete sensorimotor task can learn to perceive, select, and react as fast to ten stimuli as he can to two. Apparently, it is not the number of choices among stimuli as much as it is the number of choices among responses that slows up a subject’s processing activities and complicates his decision problems. Indeed, by limiting response alternatives (e.g., circumscribing the physical range of a trainee’s movements or providing supplementary auditory and visual indicators of error), a training device can facilitate the acquisition or transfer of skill.

Work distribution

Some generalizations can be made about work and rest in psychomotor learning: (1) massed practice is usually superior to distributed practice for simple discrete-trial tasks; (2) distributed practice is usually superior for complex continuous-action tasks; (3) short practice sessions are generally superior to long practice sessions; (4) long rest periods are generally superior to short rest periods, although forgetting must be counteracted; (5) for continuous-tracking tasks practiced under constant work sessions and variable rest periods, the final proficiency level grows curvilinearly as the intertrial interval is lengthened; (6) gains in proficiency under distributed practice, or with interpolated rest periods during massed practice, usually reflect improvements in performance rather than in learning; (7) losses in proficiency under massed practice, or with increased work load, usually pertain to inhibitory rather than motivational decrements; (8) under certain conditions (such as “cramming” for examinations) it may be most efficient to mass practice as long as adequate rest can be obtained before criterion performance is demanded; (9) reminiscence increments and warm-up decrements are intimately related to schedules of work and rest; (10) decrement is not the same as fatigue.

Quite apart from the practical question of the optimal management of training programs (e.g., in coaching oarsmen in racing shells), the aversive inhibitory consequences of sustained action that are recognized as subjective fatigue and behavioral decrement are clearly adaptive. By a reflex negative-feedback mechanism, inhibitory impulses may prevent an organism from working itself to exhaustion. With few exceptions, the presumption in favour of spaced practice can safely be taken out of the psychomotor-skills laboratory and applied in the field. Research on the skills involved in, for example, archery, badminton, basketball, golf, dancing, juggling, marksmanship, rowing, and tennis supports the notion of distributing training by means of short workouts and frequent breaks.

Motive-incentive conditions

Motivational processes are states of the organism that serve to activate reaction tendencies. Such states are classified as primary (innate) or secondary (acquired, learned) motivation. Though common physiological needs (for food, water, or avoidance of pain) may evoke psychological drives (such as hunger, thirst, or pain), the concepts of need and drive are not perfectly correlated. Some needs (e.g., oxygen demand) seem to have no specific behavioral drive, and for some drives, clear-cut biological needs remain to be identified (e.g., curiosity). Despite this apparent discrepancy, there is a theoretical consensus that psychological drive arouses the body to action, energizes its latent responses, and supports its behaviour over time. Most theorists believe that motivation (drive) and learning (habit) interact to generate a response. This implies that the same level of psychomotor proficiency may arise from quite different combinations of learning and motivation. While these theoretical interpretations often apply well to laboratory animals, their application to human acquisition of skill is complicated because incentive learning is very abstract.

Physiological explanations of human behaviour that depend on the concept of primary motives (derived from research with rats or dogs) run into difficulties in view of the fact that primary motivation and reward do not appear to be critical in most studies of human skill acquisition. Thus, instead of giving food pellets (as to a rat), an experimenter delivers praise to a human subject; rather than receiving feedback by electric shock, the human can be guided by a needle moving on a dial or a buzzer signaling an error. Despite efforts to distinguish such motivational factors as general drives from selective incentives, attempts to demonstrate significant motivational effects in human psychomotor learning have met with only modest success. Among exceptions to the above are a few studies with standard apparatus (e.g., the complex coordinator) and with special devices that have indicated that incentives or disincentives such as money, verbal threats, electric shock, exhortations, and social competition may be relevant.

Environmental factors

Many practical skills must be executed outside the laboratory under unfavourable conditions of temperature, humidity, illumination, and motion. It is generally found that, below the limiting levels of extreme stress, such conditions affect psychomotor performance to a greater extent than they affect psychomotor learning. Representative findings have included the following: (1) isolation and sensory deprivation cause dramatic reductions in vigilance and monitoring skills within an hour; (2) environmental temperatures above or below 70 ± 5 °F (21 ± 3 °C) tend to lower scores on tracking apparatus but do not impair learning; (3) oxygen deficiency slows reaction time, especially when the atmosphere corresponds to altitudes of 20,000 feet or higher; (4) accelerations of the body in a centrifuge or rotating platform disrupt postural coordination and produce systematic shifts in the perception of the vertical; (5) although such people as acrobats, dancers, pilots, and skaters can adapt well to high accelerations, even they lose equilibrium if deprived of a visual frame of reference; (6) rather mild centrifugal effects of slow, constant rotation may induce acute motion sickness and associated degradation of psychomotor proficiency in normal persons; (7) while some controlled work-rest schedules of crews during confinement in a small cabin upset daily sleep rhythms and lead to decrements in watchkeeping, memory, and procedural skills, a schedule of four-hours-on versus four-hours-off duty can be maintained for several months without significant impairment; and (8) faulty identifications of visual displays on an eye-hand matching task have been produced in volunteer subjects exposed to controlled infectious diseases (e.g., respiratory tularemia, pappataci fever, viral encephalitis).